Assessment of naturally occurring parasitism of diamondback moth in field using recruitment method

Abstract

The recent major outbreaks of diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae), in cruciferous plants in Iran has led to attempts for sustainable pest management strategies, mainly based on the natural enemies. The present study aimed to investigate naturally occurring parasitism of P. xylostella in cabbage and cauliflower fields of central Iran. For this purpose, field studies were performed to identify parasitoids of P. xylostella, and to evaluate percentage parasitism of P. xylostella using the recruitment method in main cabbage-growing areas of Isfahan province in 2009. In present study, seven species of parasitoid wasps (five larval and two pupal parasitoids) and two species of hyperparasitoid wasps were determined. The parasitoids included the braconids Cotesia vestalis (Kurdjumov), Bracon hebetor Say and Apanteles sp., the ichneumonid Diadegma semiclausum (Hellen), and the eulophid Oomyzus sokolowskii (Kurdjumov) as larval parasitoids, and the ichneumonids Diadromus collaris (Gravenhorst) and Diadromus subtilicornis (Gravenhorst) as pupal parasitoids. In addition, the pteromalids Mokrzeckia obscura Graham and Pteromalus sp. were identified as the hyperparasitoids, which in turn parasitise C. vestalis. The most predominant species were C. vestalis and D. semiclausum with the proportional abundance of 0.43 and 0.42, respectively. Percentage parasitism varied significantly between host plants, but not between areas; the parasitised proportion of P. xylostella larvae fed on common cabbage was significantly greater than that on cauliflower (0.42 vs. 0.34). The mean percentage parasitism varied between 14.5 and 68.4 for different fields, and accounted for 37.4% of P. xylostella population on an average. The greatest parasitism was achieved by C. vestalis, D. semiclausum and O. sokolowskii, with a parasitism of 21.0, 12.9 and 3.5% of field populations of P. xylostella, respectively. These findings illustrated the important role of parasitoids for sustainable management of diamondback moth.

Learning from Chemical Coping Behaviors of Wildlife to Discover New Approaches for Pest Management

“…Physical tactics, including mechanical tactics, focus on limiting access to resources of a host via employment of structural materials, which are typically preventative but can also be therapeutic (e.g., traps or trenches, Vincent et al, 2003). Biological controls are best described as the recruitment or release of a pests' natural enemies, which includes parasitoids (Afiunizadeh and Karimzadeh, 2015) and predators (Cakmak, et al 2009). Chemical tactics focus on targetspecific, reactionary, therapeutic defenses against pests using synthetic and biorational repellents and pesticides.…”

A changing world: the role of phenotypic plasticity in host-parasitoid interactions facing extreme temperatures

“…We used a set of three temperatures (22°C, 27°C and 33°C) with the latter two corresponding to temperatures exceeding the 95 th percentile of temperature distribution in the Netherlands1. We expected that under 'normal' temperature conditions, D. semiclausum to be a superior extrinsic competitor to C. vestalis, although contrasting field prevalence has been reported for both species (Afiunizadeh & Karimzadeh, 2015;Ngowi et al, 2019). We also hypothesized that D. semiclausum but not C. vestalis parasitism rate will be negatively impacted by temperature above 30°C as the former is less thermotolerant than the latter (Furlong & Zalucki, 2017;Sarfraz et al, 2005).…”

“…They have also been successfully introduced in many temperate and tropical countries as biological control agents of P. xylostella (Furlong et al, 2013;Talekar & Shelton, 1993). It has been reported that C. vestalis has a broader host range than D. semiclausum and has a more southerly distribution in the Palearctic realm, although local distributions of these two species do overlap in many areas (Afiunizadeh & Karimzadeh, 2015;Ngowi et al, 2019;Sarfraz et al, 2005;Talekar & Shelton, 1993). An initial experiment was conducted to assess the effects of parasitoid density on both intra-and interspecific competition under a 'normal' summer temperature in the Netherlands (T max = 22°C, average for 1991-2020) 2 .…”